The term “clip” in the mowing art refers to a characteristic of the operation of a reel cutting unit, namely the amount of forward travel of cutting unit 2 in the time interval determined by the length of time that it takes for successive blades on the cutting reel to contact a predetermined reference spot on the bedknife. The cutting reel has a number of helically twisted blades spaced about its circumference. As the cutting reel rotates at a substantially constant speed, any particular cutting blade will contact a reference spot on the bedknife at a predetermined time t1 with the point of contact sliding along the bedknife due to the helical twist in the blade. The next successive cutting blade on reel 10 will contact the same reference spot on the bedknife at some later point in time t2, and this process will be repeated over and over again with each successive blade. The clip is the amount the mower has moved forwardly in the time interval t2−t1.
In a walk reel mower, the ground speed of the mower as produced by the traction drive is usually a constant while mowing. Reel 10 is also driven at a constant speed while mowing to produce a consistent quality of cut. The clip is therefor determined by how fast reel 10 is rotating relative to the ground speed of the mower as well as by how many blades are carried on reel 10, whether it is an 8 bladed, 11 bladed, or 14 bladed reel, for example.
In known walk reel mowers previously manufactured and sold by The Toro Company, the assignee of this invention, reel 10 is driven by a toothed timing belt from an input shaft that mounts a toothed drive pulley. A toothed driven pulley is operatively connected to the shaft of reel 10. As the input shaft turns at a substantially constant rotational speed, the timing belt drives the driven pulley, and thus reel 10, at a driven speed that is determined by the various numbers of teeth, and thus the pitch diameters, of the drive pulley and the driven pulley. For a reel with a given number of blades, the driven speed of reel 10 is, as noted earlier, determinative of the clip for a walk reel mower that is traveling at a constant ground speed during mowing.
In this known timing belt, toothed drive pulley, and toothed driven pulley system, Toro has previously provided the user of the mower with two different toothed drive pulleys having different numbers of teeth. The user can selectively change the clip, and thus achieve a slightly different quality of cut, by replacing one drive pulley with the other alternatively usable drive pulley. However, this provides a very limited number of different clips, namely two depending upon which of the different drive pulleys is in place. Moreover, the user has to keep the different drive pulleys on hand and available in order to change the clip. If one of the alternately usable drive pulleys is lost or can't be found, the clip can't be changed.